1. Field of the Invention
This invention relates to a method for the in situ cleaning of a process chamber. Specifically, a chlorine-based cleaning is performed in a chemical vapor deposition (xe2x80x9cCVDxe2x80x9d) chamber to improve deposition process conditions and wafer-to-wafer repeatability.
2. Description of the Background Art
Semiconductor processing typically is carried out in specialized apparatus comprised of multiple chambers wherein wafers are processed by the deposition and various treatments of multiple layers of semiconductor material in a single environment. In such tools, the plurality of processing chambers and preparatory chambers are arranged in clusters, each served by robotic transfer means. Hence, such tools are commonly referred to as cluster tools. Such tools process semiconductor wafers through a plurality of sequential steps to produce integrated circuits.
Regardless of whether semiconductor processing apparatus is configured as described above or in other arrangements known to those skilled in the art, it will be appreciated that the objective is simply to process the greatest number of wafers per unit of time in the most efficient manner. However, it is characteristic of all such apparatus that active chambers, i.e. those wherein semiconductor material is deposited or treated in some other manner, such as etching, must periodically be cleaned of the residues inherently formed during such procedures. It will further be appreciated that it is desirable to have as high a throughput as possible without sacrifice of the quality of the operation carried out in a deposition chamber before it must be cleaned.
One particularly desirable feature of cleaning a deposition chamber is to perform the cleaning in situ, i.e. without the necessity of removing the chamber from the cluster tool or exposing the chamber to oxidizing elements present in the atmosphere. In situ cleaning would mean that the cluster tool would not have to be turned off while one or more chambers are cleaned. This is particularly advantageous when it is considered that chambers where different semiconductor processes are carried out become unsuitable for efficient processing at different rates and, hence, do not require cleaning at the same time. Therefore, a process whereby one or more chambers in a multiple chamber tool can be cleaned while others continue to perform their function in the process is particularly advantageous. A cleaning process that meets the needs described above is provided in accordance with the present invention.
The disadvantages associated with the prior art are overcome by the present invention of a method of cleaning a process chamber. In accordance with the present invention, wafer-to-wafer repeatability for wafers individually undergoing chemical vapor deposition of metals such as titanium or materials such as titanium nitride, is enhanced by a brief thermal cleaning step between wafers utilizing chlorine as the cleaning gas. This cleaning step significantly extends the interval, in number of wafers processed, before the deposition chamber must be cleaned. In a second aspect of the invention, the deposition chamber may be cleaned in situ by performing a first stage thermal clean utilizing chlorine as the cleaning gas and then carrying out a second stage clean by exciting the cleaning gas with a plasma. The method may also comprise the step of depositing a protective coating of material in the chamber following the two-stage deposition chamber clean. Such a protective coating is titanium that is deposited on the interior surfaces of the chamber by chemical vapor deposition and can be between about 50 xc3x85 and 1xcexc thick.
Additionally, in a system for controlling the process sequence of wafers through a semiconductor wafer processing tool containing a plurality of chambers, at least two of which are performing the deposition of titanium or titanium nitride, a general purpose computer system that operates as a special purpose controller when executing a cleaning program for such chambers performs a process including the steps of cleaning the chamber between wafers by thermally energized chlorine, monitoring the conditions in the chamber, invoking a decision to clean the chamber, performing a two-stage clean of the chamber consisting of a thermal chlorine clean followed by a plasma chlorine clean and returning the chamber to the processing sequence being carried out. The computer readable medium may further perform the additional step after the two-stage clean and prior to returning the chamber to the processing sequence of depositing a protective coating of titanium on the interior surfaces of the chamber.
With the method as described herein, wafer-to-wafer repeatability is enhanced and throughput of a wafer processing system is optimized as there is little or reduced down time for the system as a whole. The vacuum environment of the system is not broken thereby allowing wafers to be processed in another chamber while the cleaning operation is being performed in a selected chamber.